Water pumps are used in water cooled engines, primarily for operation of vehicles such as automobiles and trucks with internal combustion engines. The water pumps are typically driven by a belt attached to the crankshaft of the engine and thus operate at some percentage of engine speed. The pumps have an impeller that is used to circulate the engine coolant from the engine to the radiator and back in order to keep the coolant within acceptable temperature limits.
Efforts are being made today to reduce the power consumption of engine accessories, such as water pumps, in order to improve fuel economy and reduce emissions. A unique dual mode water pump that operates with less power, reduces engine load, improves fuel economy and reduces undesirable emissions is disclosed in U.S. Patent Application Ser. No. 61/474,928.
The water pump disclosed in Ser. No. 61/474,928 has two modes of operation, a first mode mechanical driven by the engine belt, and a second mode operated by an electric motor, such as a brushless DC (BLDC) motor. The components for the two modes of operation are contained within a housing that includes the pulley member as part of the housing. A shaft connected to the impeller of the water pump is positioned in the housing and is controlled by one mode of operation or the other, depending on certain factors.
The housing is turned at input speed by the belt of the engine positioned on the pulley member. A friction clutch assembly is positioned inside the housing to selectively allow operation of the water pump mechanically by the pulley member. A solenoid is utilized to control operation of the friction clutch assembly.
The water pump is normally driven by the electric motor throughout most of its range of operation. Where peak cooling requirements are needed, the mechanical mode of operation takes over and the water pump is driven directly by the pulley member. The friction clutch assembly can include a softening spring member which minimizes the electrical power consumed by the clutch. The dual mode cooling pump can also utilize a variable speed control which results in the use of less power.